Vredefort crater - [http://www.orangesmile.com/extreme/img/main/vredefort-crater_1.jpg]

Around 2,030 million years ago a meteor the size of a mountain (about 10km across) fell to earth in South Africa’s Free State making a crater 300km across; it is the oldest crater made by either a comet or meteorite and reportedly the site of the largest energy release in history.

In 2015, scientists claimed to have found a bigger crater (around 400km wide) underground in the Austrlian outback, although it is not visible on the earth’s surface.